linux-kernel - Possible x2apic breakage

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Date:	Thu, 29 Jan 2009 09:41:46 -0600
From:	Jack Steiner <steiner@....com>
To:	suresh.b.siddha@...el.com
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Possible x2apic breakage

Suresh -

This popped up in Ingo's x86 tree yesterday. This appears to be breaking
on our simulator running in x2apic mode. If I understand the code,
this is a real breakage and not a problem in our simulator:

arch/x86/include/asm/genapic.h

	static inline unsigned int read_apic_id(void)
	{
        	unsigned int reg;

        	reg = *(u32 *)(APIC_BASE + APIC_ID);
        	return apic->get_apic_id(reg);
	}

As expected, the failure occurs right after:

	Enabling x2apic
	Enabled x2apic and interrupt-remapping

The next reference to apicid tries to read from mem instead of MSRs.

--- jack

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